Referring now to FIGS. 1 through 4, there is shown the normal sequence of operation for a typical 4-cycle internal combustion engine. On the intake stroke (FIG. 1), an explosive mixture of vaporized fuel, such as gasoline, and air is drawn into the cylinder 10 through the open intake valve 14 as the piston 12 moves downward. On the compression stroke (FIG. 2), the intake valve 4 is closed and the piston 12 rises to compress the fuel-air mixture. On the power stroke (FIG. 3), the compressed fuel-air mixture is fired or ignited by an electric arc across the gap of a spark plug 18, thereby propelling the piston 12 downward. On the exhaust stroke (FIG. 4), the piston 12 travels upward expelling the burned gases through the open exhaust valve 16. After the burned gases have been expelled and the exhaust valve 16 closes, the piston 12 moves downward and the cycle is repeated.
A major disadvantage of such conventional internal combustion engines is the inability of the electric spark to generate an instant flame front with sufficient magnitude to provide efficient combustion of the fuel-air mixture. This incomplete combustion is characterized by a high percentage of unburned hydrocarbons resulting in wasted fuels and polluting gases which are discharged into the atmosphere.
Heretofore, prior art devices have attempted to eliminate these disadvantages by utilizing auxiliary or precombustion chambers. The prior art pre-combustion chambers, such as described in U.S. Pat. No. 3,066,661, function to ignite a fuel-air mixture which has a concentration that may be different from the fuel-air mixture in the main combustion chamber.
These prior art pre-combustion chambers suffer due to the following disadvantages. Firstly, such pre-combustion chambers must be of a sufficient size to hold the relatively large volume of fuel and air required to create a flame front of sufficient magnitude to cause complete combustion of the fuel-air mixture in the main chamber. Secondly, such large volume pre-combustion chambers make complete purging after firing difficult.